The studies will focus on the description of antigenic epitopes on protein I and protein III. We have a large number of clones producing antibodies to PIB proteins and we have the sequence of a PIB gene nearly complete. Using deletion mutants and synthetic peptides the reactive eptiopes will be defined. It has recently been demonstrated that human antibodies to PIII are able to block bactericidal activity of antibodies directed to other surface antigens. We have completed the sequence of the structural gene of PIII and this has allowed the proposal of a model of the disposition of this protein in the outer membrane. We are currently isolating PIII reactive monoclonal antibodies and will determine the antigenic epitopes of PIII, their surface exposure, and which one generates the blocking antibodies.